What have teeth. Inside every clock there's a set of gears - wheels with teeth. When one of the gears turn, it pushes another. One gear is exactly the size and speed that makes the minute hand go around a dial every 60 minutes. Another gear makes the hour hand go around every 12 hours, says 3-2-1 Contact magazine.
But something's got to make the wheels turn, right? Right! Clocks get their power from all sorts of things. A hanging weight or a swinging weight, called a pendulum, can make a clock go.A spring that you wind powers many watches. In other watches, a battery causes a piece of quartz or a metal fork to vibrate. This creates electricity that turns the wheels. Other electric clocks just plug into the wall. Last but not least are digital clocks - they're actually tiny computers programmed to count the hours, minutes and seconds.